Graduation shoot-need help

[goodguy]

...There is no particular advantage to holding to a low ISO. ISO has nothing to do with exposure, only with the image that the camera will produce. I would set the ISO to "auto" or set a maximum setting, based on the camera's ability to deal with a lower signal-to-noise ratio (S/N). Do some testing with your camera to find out how much noise you get with each ISO setting. I seriously doubt if your shot will be spoiled by noise alone.

Ummmm... I would respectfully disagree. Given that this is a graduation photo, it's entirely likely that some will want to print it, and potentially at larger sizes. As well, given how small each face is going to be, even a bit of excess noise is going to have an effect as people zoom in to see themselves. You also need to consider exposure. It's a virtual certainty that some people will require local exposure adjustment due to shadowing, and increasing exposure on an already high ISO is a great way to turn an image to junk. Rather than allowing the camera to use auto, do some experimenting with your gear so that you know exactly what results you can expect at a given ISO, and keep it as low as practical.

All event pictures need to be printed 5x7 as the contract states

 

[Derrel]

I would consider using one single main light, placed very high up and angled downward so that the light casts an under-chin shadow and an under-nose shadow on every face, and the light positioned so that the shadow from the people in the first row (and other rows) falls down and behind and does not land on the face of the person behind!

This is a very old -ime professional banquet and team photo strategy. The single, high,downwardly-angled main light mimics the sun. There's no need for a fill light. There are no competing cross shadows. At 20 to 25 feet the light will be even and without fall off. At 25 to 30 feet, even the largest umbrella becomes in effect a fairly hard source. Diffusing the light is counterproductive. I would take two or three speed lights and tape them together and use them as the one single main light and remember –position the light high and angled downward!